Signs of a Dirty or Faulty Fuel Filter

replacing a fuel filter

The fuel filter is often a forgotten feature of your vehicle. Like all filtration systems, it will fail over time as it becomes increasingly clogged with all the particles it’s blocking. You might think of fuel as fairly clean, but even at the pump, fuel can contain many impurities such as dirt, rust from the storage tanks or even chips of paint.

The filter prevents contaminants from reaching the engine, which could impact its performance and shorten its lifespan. How can you ensure your filter is working properly at all times – and also tell when it’s on its way out?

The purpose of the fuel filter

The car’s fuel system draws fuel from the tank, and then passes it through the fuel filter for distribution to the engine, via the injection system or carburettor. It’s then spent as the product of combustion in the engine’s cylinder chambers, with each carefully timed ignition providing the energy needed for motion. The fuel filter forms an essential barrier, preventing dirt such as fuel impurities or rust from entering into the engine. If foreign matter does surpass the filter and enter the engine, this can cause premature wear, damage and a loss in fuel efficiency.

In the last decade fuel filters have become increasingly important as modern car designs use ever more efficient engines. The filter is an essential part that prevents damage in the engine, which could be extremely costly to repair. It’s therefore in the best interests of both your car and your bank account that you keep the filter in good working order.

in line fuel filter

Problem signs

Difficulty starting your vehicle

One of the first problems you’re likely to experience with a dirty of failing filter, is trouble starting the car. A clogged filter will deliver a reduced volume of fuel to the engine, resulting in hard starting. If left unchecked over time, then this will completely stop your car from starting.

Poor fuel economy

Your engine is a finely balanced system, controlled by computers that govern the fuel flow into the combustion chambers of the pistons. When the fuel flow is irregular, thanks to a blocked or failing fuel filter, this can mean the incorrect volume of fuel is supplied to the engine, resulting in either unburned fuel or a drop in performance – either will reduce the car’s fuel economy.

Check engine light

The check engine light is a great indicator that the engine is suffering from issues – such as poor fuel flow and a reduction in overall efficiency, both of which can result from a dirty fuel filter. This is an especially useful indicator that you need to have your fuel filter inspected by a mechanic, when accompanied by other symptoms on this list.

Strong odours

If your fuel filter is blocked, clogged or broken, then it could be both impacting the proper flow of fuel into the engine. If it is broken however, then it could also easily start leaking fuel creating strong odours around the car. This is a serious symptom and even if you don’t suspect the fuel filter, we’d recommend visiting a mechanic, if you smell fuel anywhere around your vehicle.


As the fuel flow through a dirty or broken filter becomes increasingly constricted, insufficient fuel reaches the engine. This can be especially problematic when moving the car from a stopped position, as the engine requires more energy to overcome the inertia of the motionless vehicle – often resulting in the engine stalling. Additionally, you may notice stalls immediately after starting the car.

replacing a fuel filter cartridge

Decrease in power and performance

Out on the open road, a dirty or broken fuel filter will impact the overall performance of the engine, resulting in a decrease in power, which will be especially noticeable under acceleration. This may even be picked up by the internal computer, throwing the car into a special “limp mode” where the vehicle’s speed will be severely reduced to protect the engine. Cars are not supposed to drive in limp mode for extended periods of time, so if this happens you should seek out a mechanic immediately.


An inconsistent flow of fuel to the engine through the dirty or broken fuel filter can cause the engine to misfire, especially under acceleration. You might also experience shakes and shudders at different speeds, as the engine struggles to achieve the flow of fuel necessary to operate effectively.

Damaged fuel pump

If your fuel filter is damaged or clogged up, it will put more strain on your fuel pump as the pump works harder to push more fuel through to the engine. If you find that your pump is faulty, then it’s definitely worth having a look at the filter, to check whether or not this is the cause of the failure.

And finally

If you are having problems with the fuel filter, it makes sense to try to unclog and clean it before you go any further. However, if this has no effect on the engine’s performance, then it’s not too difficult to replace your vehicle’s fuel filter with a little mechanical knowledge.

Regular checks will also help ensure that the part is not blocked – and considering the damage that a clogged filter can inflict on your engine – it will also help you save money on engine repairs. However, the part does have a limited lifespan, and will need changing eventually.

This entry was posted in Maintenance on by Justin Smith.

About Justin Smith

As the man at the helm of BreakerLink, it is no surprise that its Director, Justin Smith, has always had a keen interest in cars, bikes and most things wheeled. Having spent over two decades in the car parts industry, Justin combines his passion that since 2002, has successfully united those looking for new and used car parts with the breaker that supplies them. Follow Justin on LinkedIn.

Disclaimer: These articles are for guidance purposes only. If you have any questions regarding any matter relating to your vehicle we would recommend that you seek the advice of an appropriate professional. We accept no responsibility or liability should you suffer financial or personal damages in relation to the advice stated on this website.